t r C eUt$ U Jim Potro THERE ARE AS MANY airfoil shapes tax laws Did know has two versions first pure plot curves generated wind tunnel tests second expressed feelings flight results after airfoil wing/flying machine components combined Anyone can begin myth airfoil aeronautical achievement Some years ago modeler/aero alchemist put paper observed experience tow-launched sailplane climbs higher can reasonably expected hypothesis contends wondrous modification rectifies airflow over wing top surface augments generation lift secondary benefit new shape much greater angle-of-attack AOA wing can rotated before stall occurs indented terracelike depressions rear half top surface surmised condition reversed airflow start stall being hindered moving forward similar affect bird wing feathers curl up high AOA Something wasnt quite right mind about newfound lift proposed science fair project son study terraced airfoil TAF gave Chris three very productive years continuing research knowledge also demonstrated eye can fool mind Tests proved terraces did indeed improve stalling no way Bernoullis theorem danger lift doesnt exist What observed glider shooting skyward higher AOA normal fact terraces permitted glider go up like superkite because no normal stall high AOA wind Air reverse-flow rapidly undercuts lift production STANDARD Air reverse-flow inhibited terrace step TERRACED Air lifts feathers creating high lift drag BIRD AIRFLOW STALL COMPARISONS Figure 2 February 1995 53 Standard Smooth Airfoil 50%5 Equal Spaces Terraced Airfoil Comparison tested ace foam airfoils Figure 1 tunnel tests produced curves showing top surface lift never exceeded unmodified airfoil lift could actually reduce lift 10% too terraces used final proof lay flight tests glider optimum terraces incorporated left wing right side smooth Videotape analysis clearly shows exactly what anticipated Straight flight normal no apparent yaw drag imbalance Applied up-pitch started normally until about 75% pre-stall AOA TAF entered its realm modified lift standard airfoil still linearly increasing liftThe airplane predictably began left roll imbalanced lift because TAF producing less right side standard wing Continued up-elevator brought AOA past standard wings stall point dihedral effect together both sides now generating almost equal lift began rolling plane back wings-level As AOA continued increase TAF just reaching maximum lift before loss gradual stall wings lift imbalance rolled toward fully stalled standard side Recovery simple stickforward regain speed attitude Would want fly TAF wing multitude ways make terrace indentions five evenly spaced rearward starting 50% chord point optimum next level investigation should determine terminate terraces wingtip would very easy apply TAX molded foam wing Ace High glider Myths usually form distorted truth Some airfoils precisely shaped Clark Eppler Grant Selig others Nature works flying birds fish insects seeds squirrels snakes An intriguing government airfoil test report states top curve aifflow never catches up lower airflow Bernoulli claims should happen declares separation trailing edge about equal difference upper lower surface lengths now have choice projectto de-myth Bernoulli probably never flew model airplane government Technical review article done Larry Conover published TGX terraced-airfoil HLG 1960s comments looks good. TGX design attempt prevent creeping boundary layer detaching airflow wing causing stall worked because could adjust higher glide angle smoother flight path However apparently resulted bit drag dead-air time no better standard version fly turbulent contest conditions stable airfoil definite advantage al Level Recovery / / Right roll until terraced side stalls Roll right level standard side stalls Normal straight glide Apply up-elevator pitch-up stall AOA Flight Path Test Glider Figure 4 Blend terraces back dump low-pressure tip vortex Terraced Outer part control tip-stall wash-in Tapered terrace handle air flow volume moving wing tip -9 Put terraces both top bottom uniform acrobatic flying . Terraces end tip IDEAS FOR TERRACES TERMINATIONS AND PLACEMENTS Figure 5 Left roll begins 75% pre-stall AOA pitch-up 54 Model Aviation 4T Same maximum Lift e 0 U a 0 E 0 3I -J II Ij 0 Angle Attack LIFT VS AOA CURVES Figure 3
Edition: Model Aviation - 1995/02
Page Numbers: 53, 54
t r C eUt$ U Jim Potro THERE ARE AS MANY airfoil shapes tax laws Did know has two versions first pure plot curves generated wind tunnel tests second expressed feelings flight results after airfoil wing/flying machine components combined Anyone can begin myth airfoil aeronautical achievement Some years ago modeler/aero alchemist put paper observed experience tow-launched sailplane climbs higher can reasonably expected hypothesis contends wondrous modification rectifies airflow over wing top surface augments generation lift secondary benefit new shape much greater angle-of-attack AOA wing can rotated before stall occurs indented terracelike depressions rear half top surface surmised condition reversed airflow start stall being hindered moving forward similar affect bird wing feathers curl up high AOA Something wasnt quite right mind about newfound lift proposed science fair project son study terraced airfoil TAF gave Chris three very productive years continuing research knowledge also demonstrated eye can fool mind Tests proved terraces did indeed improve stalling no way Bernoullis theorem danger lift doesnt exist What observed glider shooting skyward higher AOA normal fact terraces permitted glider go up like superkite because no normal stall high AOA wind Air reverse-flow rapidly undercuts lift production STANDARD Air reverse-flow inhibited terrace step TERRACED Air lifts feathers creating high lift drag BIRD AIRFLOW STALL COMPARISONS Figure 2 February 1995 53 Standard Smooth Airfoil 50%5 Equal Spaces Terraced Airfoil Comparison tested ace foam airfoils Figure 1 tunnel tests produced curves showing top surface lift never exceeded unmodified airfoil lift could actually reduce lift 10% too terraces used final proof lay flight tests glider optimum terraces incorporated left wing right side smooth Videotape analysis clearly shows exactly what anticipated Straight flight normal no apparent yaw drag imbalance Applied up-pitch started normally until about 75% pre-stall AOA TAF entered its realm modified lift standard airfoil still linearly increasing liftThe airplane predictably began left roll imbalanced lift because TAF producing less right side standard wing Continued up-elevator brought AOA past standard wings stall point dihedral effect together both sides now generating almost equal lift began rolling plane back wings-level As AOA continued increase TAF just reaching maximum lift before loss gradual stall wings lift imbalance rolled toward fully stalled standard side Recovery simple stickforward regain speed attitude Would want fly TAF wing multitude ways make terrace indentions five evenly spaced rearward starting 50% chord point optimum next level investigation should determine terminate terraces wingtip would very easy apply TAX molded foam wing Ace High glider Myths usually form distorted truth Some airfoils precisely shaped Clark Eppler Grant Selig others Nature works flying birds fish insects seeds squirrels snakes An intriguing government airfoil test report states top curve aifflow never catches up lower airflow Bernoulli claims should happen declares separation trailing edge about equal difference upper lower surface lengths now have choice projectto de-myth Bernoulli probably never flew model airplane government Technical review article done Larry Conover published TGX terraced-airfoil HLG 1960s comments looks good. TGX design attempt prevent creeping boundary layer detaching airflow wing causing stall worked because could adjust higher glide angle smoother flight path However apparently resulted bit drag dead-air time no better standard version fly turbulent contest conditions stable airfoil definite advantage al Level Recovery / / Right roll until terraced side stalls Roll right level standard side stalls Normal straight glide Apply up-elevator pitch-up stall AOA Flight Path Test Glider Figure 4 Blend terraces back dump low-pressure tip vortex Terraced Outer part control tip-stall wash-in Tapered terrace handle air flow volume moving wing tip -9 Put terraces both top bottom uniform acrobatic flying . Terraces end tip IDEAS FOR TERRACES TERMINATIONS AND PLACEMENTS Figure 5 Left roll begins 75% pre-stall AOA pitch-up 54 Model Aviation 4T Same maximum Lift e 0 U a 0 E 0 3I -J II Ij 0 Angle Attack LIFT VS AOA CURVES Figure 3